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ATENT FREDERICK W. GESSVVEIN, OF BROOKLYN, NEW YORK.

BROACl-i.

SPECIFICATION forming part of Letters Patent N0. 363,059, dated May 17. 18 87.

Application filed August 19, 1886.

To all whom it may concern:

Be it known that I, FREDERICK WV. Gnss WEIN, a citizen of the United States, residing at Brooklyn, county of Kings, and State of New York, haveinvented certain new and useful Improvements in Broaches, fully described and represented in the following specification and the accompanying drawings, forming a part of the same.

This invention relates to that class of tools known more particularly to the watch-case trade as broaches. It may be stated, however, that a broach is similar to a reainer, in that it is used for the purpose of smoothing or finishing out a hole, which, from the nature of its use, neccessitates great accuracy for fitting purposes. In watch cases, for instance, the knuckles of the joint or hinge between the caps and center are required to be fitted with nicety and to be in perfect alignment, so that the pin which is to complete the hinge will fit snugly in the knuckles, permitting, however, the caps to be opened and closed easily.

As a ready understanding of the invention can be best given bya description thereof, reference will now be had to the accompanying drawings, in which- Figure 1 illustrates by a side elevation the improved broach, greatly enlarged; and Fig. 2, a cross-section thereof, still more enlarged,

while Fig. 3 is a similar view illustrating the old form of broach.

Broaches are usually formed of square steel wire that is cut off into suitable lengths, and after being shaped to give them a slight taper and otherwise prepared have their surfaces Serial No. 211,310. (No model.)

ground flat, and thus leave their edges, as 2, comparatively sharp, as seen in Fig. 3.

The object of the present invention isto provide a broach that will be better adapted for finishing purposes than those heretofore made; and to this end it consists in the improved breach now to be particularly described. It may be formed of square steel wire, as heretofore, and be otherwise prepared for the grinding operation; but instead of having its surfaces ground perfectly flat, said surfaces will each be ground concave, as seen at 3 in Fig. 2, extending the entire width of the broach, so as to provide the edges 1. This concaving will preferably extend from the point 4 of the broach down to within a short distance of its butt-end, so as to leave a suitable shank, 5, to be grasped by aholder or handle.

It will thus be readily seenthat a broach made in this manner presents much keener edges than those heretofore made, and which will obviously keep in shape for use much longer than thoseground fiat, whose edges wear round very quickly.

WVhat I claim is- The herein-described broach, having each of its surfaces concaved from edge to edge in width, and extending substantially their entire length, as set forth.

In testimony whereof I have hereunto set my hand in the presence of two subscribing witnesses.

r. w. ensswnnv.

\Vitnesses:

Gno. H. GRAHAM, T. H. PALMER. 

